A variety of display devices having a touch sensor have been conventionally proposed. Such a display device includes, for example, an array substrate, a counter substrate arranged above the array substrate, a plurality of columnar spacers provided between the counter substrate and the array substrate, and a switch unit formed on the lower surface of the counter substrate. The spacers are made of an elastically deformable resin, and are members for maintaining a constant cell thickness between the array substrate and the counter substrate.
The switch unit includes a projection projecting from the lower surface of the counter substrate toward the array substrate, a counter electrode formed to cover the projection, and a lower electrode formed on the array substrate.
The projection is formed by arranging a resin or the like on the counter substrate, and subsequently patterning the resin. The projection has a height lower than that of the spacers, and the counter electrode positioned on the projection and the lower electrode are spaced apart from each other when the counter substrate is not being pressed. When pressed by a user, the counter substrate sags and the spacers are elastically deformed, causing the counter electrode positioned on the projection to come into contact with the lower electrode.
In such a display device with a touch panel function, the projection needs to be formed with an accurate height. Unfortunately, in the process of forming the projection, it is difficult to form a resin of a uniform thickness on the surface of the counter substrate, and slumping tends to occur during patterning of the formed resin. It is thus difficult to form the projection with an accurate height, and the formed projections tend to vary in height. The height variation among the projections may make it difficult for the switches to function, or may cause the switches to be turned on even if the counter substrate is not being pressed, for example, resulting in difficulty in ensuring reliability of the switches.
The projection is formed by patterning the resin as described above, and the peripheral surface of the projection rises to be substantially perpendicular to the array substrate. When the counter electrode is formed on the surface of the projection, the counter electrode may be torn.
A display device aiming to suppress such tear of a counter electrode has been proposed. For example, a liquid crystal display device described in Japanese Patent Laying-Open No. 2007-58071 (PTL 1) includes an array substrate, a counter substrate provided above the array substrate, and a plurality of touch sensors provided on the upper surface of the array substrate.
The touch sensors each include an insulative tubular sensor projection, and a conductive layer formed within the sensor projection. The conductive layer has a lower end portion connected to a pixel electrode. The conductive layer has an upper end portion which is recessed from an opening of the tubular sensor projection toward the inside of the sensor projection.
The sensor projection has an upper end portion in contact with the counter substrate, and is made of an elastically deformable material. When the counter substrate is pressed, a cell thickness between the array substrate and the counter substrate is reduced and the sensor projection is elastically deformed, causing the upper end portion of the conductive layer to come into contact with a counter electrode formed on the counter substrate.